Widening the scope of rack-and-pinion

Stober's product range includes four distinct types: ZR, ZTR, ZTRS, and the newest member of the "Zeries", the ZV. The "ZV" rack-and-pinion system is an economy design which uses a shaft-mounted pinion without support bearings. This system is suitable for applications that don't require high accuracy gearbox shafts. An optional adjustment plate can be used for easy installation. The ZV is available for multiple gearbox styles and has an optional self-contained lubrication system.

ZV rack-and-pinion drives are DIN quality 7 and come in Modules 2, 3 and 4. The maximum feed forces have a range from 1.1 to 17kN, depending on the unit and the pinion. The linear backlash goes as low as 20 microns. Since they are shaft-mounted, the ZV pinions can mount to Stober's inline P and PE or its right-angle, K, KL or KS gearbox shafts. The units are also offered with an adjustment plate, allowing for easy installation and meshing of the pinion to the rack. The adjustment plate allows the gear unit and pinion to be raised or lowered between full tooth engagement and no tooth engagement.

Pinions & options

For the gear units in the P/PA/PK/PKX/PE/KS/K/KL series, the pinions on the rack-and-pinion drives are supplied in a backlash-free shaft-hub connection (shrinkfit and keyed). For accurate mounting and for lubrication of the rack-and-pinion system optional accessories are available:

Setting plates - There are specific setting plates for mounting and positioning of the different rack-and-pinion drives. Positioning can be made easier by an optional adjustment device;

Lubrication - A felt gear (with mounting kit) is used to lubricate the pinion or alternatively the rack. The grease can be supplied either decentrally via an automated lubricator or via a central lubricant supply;

Clamping set - For the gear unit models P5, P7, PE5, K2, K3 and K4, it is possible to attach the pinion with a clamping set.

Older cousins

Of the more established versions, the "ZR" features a design with a large helical gear mating directly to the rotating flange. It is ideal for high speed applications.

The "ZTR" rack-and-pinion system uses a flanged pinion without support bearings, and is suitable where the support housing has an interference. The pinion gear can easily be changed or removed. The mass moment of inertia ratios may be optimally adapted by varying the gear ratios and/or the number of pinion teeth.

Finally, the "ZTRS", as reported in CDA in the Oct/Nov 2012 issue, and shown in the picture, arises from a collaboration of Stober and Atlanta, a premier manufacturer of gear racks. It is a premium product aimed at very high torque, torsional stiffness, and tilting moment requirements. This design consists of a support housing with a flanged pinion, optional felt gear for lubrication, and a PH or PA gear.

The most immediately striking feature of the new HighForce ZTRS-PH(A) rack-and-pinion drive is the integral output bearing housing, a highly stiff supporting assembly for the rack pinion which relieves the load on the flange-mounted planetary gear unit bearings. The reduced tilting moment of this construction makes it possible to base the drive design on the torque actually required and on the feed force.

As a rule this means that the gear unit can be a size smaller than normally used in the past. Due to the comparatively small pinions, a higher output speed is necessary to obtain the required feed rate. Which means that the gear ratio is lower and in many cases a single-stage planetary gear unit can be used instead of a two-stage.

This gives the outstanding power density that should encourage many designers to use redesigned rack-and-pinion drives.